1. Field of the Invention
The present invention relates to a variable tappet. More particularly, the present invention relates to a variable tappet that can vary valve lift according to an engine operation condition.
2. Description of Related Art
An internal combustion engine generates power by burning fuel in a combustion chamber in air media drawn into the chamber. Intake valves are operated by a camshaft in order to intake the air, and the air is drawn into the combustion chamber while the intake valves are open. In addition, exhaust valves are operated by the camshaft, and a combustion gas is exhausted from the combustion chamber while the exhaust valves are open.
An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, an optimal lift or optimal opening/closing timing of the valves depends on the rotation speed of the engine. In order to achieve such an optimal valve operation depending on the rotation speed of the engine, various researches has been undertaken. For example, research has been undertaken for a variable valve lift (VVL) apparatus that enables different lifts depending on an engine speed, and for a variable valve timing (VVT) apparatus that opens/closes the valves with different timing depending on the engine speed.
A variable valve lift (VVL) apparatus can be divided into two variable valve lift apparatuses. One type of the apparatus is to control operations of a swing arm and the other type of the apparatus is to vary tappet for varying valve lift.
In the variable tappet type, more than two locking pins, which have to be used to each inner and outer tappet body, are needed and hydraulic lines and guides for controlling the locking pins are also needed.
Also, a stopper and so on, which prevents the locking pin or a connecting pin from separating by a return spring, is needed. And if a tappet is formed as a cylinder shape, an auxiliary element for preventing rotation of the tappet is required.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.